Prader-Willi Syndrome

Test name:  Prader-Willi Syndrome (PWS) Testing
Also known as: Methylation 15, Deletion/duplication 15q11-q13 by FISH or microarray, Uniparental disomy (UPD) by UPD Array 

Indications: Clinical features of Prader-Willi syndrome may include feeding difficulties and severe hypotonia in infancy with excessive eating and development of obesity in later infancy or early childhood. Delays are often noted with both motor and language skills with some level of intellectual impairment seen in all individuals with PWS. Common behaviors noted may include temper tantrums, OCD, and stubbornness. Individuals with PWS often have characteristic facial features, strabismus, scoliosis, short stature, hypogonadism in both genders, and infertility. 

Test Information: PWS is caused by absence of the paternal copy of the PWS/Angelman syndrome region of chromosome 15. A combination of methylation, FISH, chromosomes and/or UPD will detect a genetic abnormality in ~99% of individuals with PWS; this lab does not perform sequence analysis on the imprinting center which is the cause for less than 1% of individuals with PWS.

Name of Test Method Additional information
Methylation 15
  • Methylation specific PCR for the PWS critical region following bisulfite modification of DNA
Deletion/Duplication analysis
  • Approximately 70% of individuals with PWS will have a deletion detected by FISH, high resolution chromosomes, or array (180K Microarray or UPD Array) of the AS/PWS critical region
  • Recurrence risk is less than 1% with a deletion
Uniparental disomy (UPD) study
  • UPD Array will identify most deletions of 15q11-q13 AND most whole-chromosome and segmental paternal UPD associated with PWS
  • Approximately 25-29% of PWS is due to paternal UPD plusit will detect deletions seen in 70-75% of individuals with PWS
  • Recurrence risk is less than 1% with UPD or deletion
Chromosome Analysis  

Additional tests available on postnatal samples (refer to additional pages for details):
     Single gene testing – refer to Test Catalog for tests offered at HGL
     Coming soon: Next Generation Sequencing

Specimen requirements:

  • One 2-5 ml whole blood sodium heparin (green top) tube AND one 2-5 ml whole blood EDTA (purple top) tube*
    *If newborn/limited blood – one sodium heparin (green top) tube with 1ml minimum

CPT codes:

  • Methylation: 83890(x4), 83891, 83892(x4), 83894(x4), 83896(x4), 83898(x2), 83900(x2)
  • Postnatal FISH:
    • Age 0-3 months: One chromosomal target: 88230, 88271(x1-3), 88275, 88291

      For each additional chromosomal target: 88271(x1-2), 88275(x0-1) plus the “One chromosomal target” CPT codes listed above

    • Age 3+ months: One chromosomal target: 88271(x1-3), 88272, 88275, 88291

*If concurrent G-bands studies are NOT being performed, add 88230 to the “One chromosomal target” CPT codes.

  • 180K Microarray: 83892(x2), 88230, 88271(x16), 88386**
  • UPD Array: 83892(x2), 88230, 88271(x16), 88386**
  • Postnatal Chromosome Analysis: 88230(x2), 88261, 88280(x2), 88285(x3), 88289

**Unless using stored DNA from a prior sample, the following DNA Extraction codes (83891, 83894, 83907, 84311) will apply once for microarray/molecular testing.

Pricing: Contact the laboratory billing staff for current costs

Shipping & Handling 

Required forms: Postnatal Test Request Form 

Turn-around time (times are estimates and may change with volume):

  • Methylation: 4 weeks
  • Postnatal FISH: 7 days
  • 180K Microarray: 1-2 weeks
  • UPD Array: 1-2 weeks
  • Postnatal Chromosome Analysis: 7-10 days

References: GeneReviews 

Revised: 7-3-12

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